As used herein, “electric vehicle” means an automotive vehicle having an electric powertrain and includes what is commonly known as a battery electric vehicle having only the electric powertrain and a hybrid electric vehicle having an electric powertrain and convention internal combustion engine powertrain.
FIG. 1 is a simplified diagram of a prior art electric vehicle 100 having a high voltage module 102. High voltage module 102 is powered by two direct current supplies, a high voltage direct current supply 104 and a low voltage direct current supply 106 and is electrically connected to them in conventional fashion with electrical conductors such as copper wire. High voltage supply 104 is for example a 350 volts direct current battery pack 108. Direct current is sometimes referred to herein as DC, volts direct current is sometimes referred to herein as VDC, alternating current is sometimes referred to herein as AC and volts alternating current is sometimes referred to herein as VAC. Low voltage supply 106 includes for example a conventional 12 VDC battery 110 of the type used for automotive vehicles. In a hybrid electric vehicle, low voltage supply 106 typically also includes an alternator.
High voltage module 102 has a low voltage section 112, a high voltage section 114 and isolation barrier electrically isolating low voltage section 112 from high voltage section 114. Isolation barrier 116 includes, for example, one or more isolating DC/DC converters 117 that provide low voltage DC from low voltage supply 106 to high voltage section 114 that is isolated from the low voltage DC from low voltage supply 106. This low voltage DC provides low voltage DC power such as to power logic devices of high voltage section 114 that require low voltage DC. This low voltage DC provided to high voltage section 114 in an example includes 12 VDC and 5 VDC. The low voltage DC from low voltage supply 106 on the low voltage side of isolation barrier 116 is electrically connected to electronic devices in low voltage section 112 representatively shown by PCB 113. The low voltage DC on the high voltage side of isolation barrier 116, for example, the output(s) of the DC/DC converter(s) 117, is electrically connected to electronic devices in high voltage section 114 representatively shown by PCB 115.
Motor 118 is electrically coupled to high voltage section 114. Motor 118 is illustratively an AC motor and high voltage section 114 includes an inverter (not shown) that inverts the high voltage DC from high voltage supply 104 to AC that is output to motor 118. The inverter includes power switching semiconductors that are controlled by one or more control logic devices of low voltage section 112, shown representatively by PCB 113. Low voltage section 112 (e.g. the control logic devices) is powered by low voltage, such as 12 VDC from low voltage supply 106 as is an electronic motor control unit referred to herein as EMCU 120. Low voltage section 112 is thus considered a low voltage section. EMCU 120 is logically coupled to low voltage section 112 of motor power module 102, such as by data bus 122, a controller area network bus for example. Controller area network is referred to herein as “CAN” and a controller area bus is referred to herein as a CAN bus.
While low voltage supply 106 supplies the low voltage power for the electronic devices of high voltage section 114 that are powered by low voltage, the low voltage supply 106 and low voltage power of high voltage section 114 do not have common grounds. This is done for safety purposes, but presents complications in the design of the interface between the low voltage section 112 and the high voltage section 114 since high voltage module 102 must then have two separate grounds, one for low voltage section 112 and one for high voltage section 114. To transfer data, control signals, etc., between low voltage section 112 and high voltage section 114, isolation barrier 116 is required to provide the requisite electrical isolation between low voltage section 112 and high voltage section to electrically isolate low voltage section 112 from the high voltage supply 104, and thus also electrically isolate the low voltage power and other components of the vehicle 100 electrically connected to the low voltage power, such as EMCU 120, from the high voltage section 114. Further, vehicle 100 must have both high voltage cabling to transfer the high voltage power, such as from high voltage supply 104 to high voltage section 114 and from high voltage section 114 to motor 118 and also low voltage cabling to transfer the low voltage power, such as from low voltage supply 106 to low voltage section 112 and EMCU 120. In this regard, the low voltage cabling includes electrical conductors such as copper wire that electrically connect the low voltage supply 106 to low voltage section 112, such as a positive electrical conductor and a ground electrical conductor. The high voltage cabling includes electrical cables having electrical conductors that electrically connect the high voltage supply 104 to high voltage section 114.